1. Field of the Invention
Aspects of the present invention relate to a light scanning system and an image forming apparatus including the same, and more particularly, to a light scanning system including a small optical system having improved curvature characteristics and an image forming apparatus including the light scanning system.
2. Description of the Related Art
One or more light scanning systems are used in an image forming apparatus (e.g., a laser printer) to form an electrostatic latent image by scanning a laser beam onto a photosensitive medium of the laser printer. Since a black and white laser printer transfers only black ink droplets onto paper, only one organic photoconductive (OPC) drum is required. In contrast, since a color laser printer transfers black, magenta, yellow, and cyan ink droplets onto paper, four light scanning systems and four OPC drums are required. The light scanning system greatly affects the manufacturing cost and image quality of a color laser printer. Accordingly, the number of components used in the light scanning system should be reduced to lower the manufacturing cost of the color laser printer, and the optical performance of the light scanning system should be improved to increase printing quality. In particular, the manufacturing cost of the image forming apparatus can be reduced by employing only one deflector. One deflector used in a color image forming apparatus may scan a plurality of light beams onto photosensitive members corresponding to a plurality of colors in two ways.
FIG. 1 is a cross-sectional view of a light scanning system 9 disclosed in Japanese Patent Laid-open No. 2004-021133. Referring to FIG. 1, the light scanning system 9 projects a plurality of parallel light beams E1, E2, E3, and E4 at different heights in a sub-scanning direction to a deflection surface of a deflector 4. Then, the light beams E1, E2, E3, and E4 are imaged onto corresponding photosensitive drums 1. A plurality of mirrors 7a, 7b, and 7c, and f-θ lenses 5 and 6 are disposed in optical paths between the deflector 4 and the photosensitive drums 1 in order to direct the light beams E1, E2, E3, and E4 to the corresponding photosensitive drums 1. However, since the light beams E1, E2, E3, and E4 are directed at different heights, the deflector 4 has an increased thickness and the f-θ lenses 5 and 6 have larger effective surfaces, thereby making it difficult to manufacture the light scanning system 9 compactly.
FIG. 2 is a cross-sectional view of another light scanning system disclosed in Japanese Patent Laid-open No. 2004-021133. Referring to FIG. 2, a plurality of light beams E1, E2, E3, and E4 are obliquely incident on a deflection surface of a deflector 4. However, in this case, scan lines are curved on objects onto which the light beams E1, E2, E3, and E4 are scanned. To reduce and correct the curvature of the scan lines, two or more f-θ lenses 13 and 14 are disposed in each optical path. Also, since a plurality of reflective mirrors 12a, 12b, and 12c are disposed between the f-θ lenses 13 and 14 and photosensitive drums, the scan lines may be skewed when the reflective mirrors 12a, 12b, and 12c are assembled.